﻿package com.shuqi.common.utils;

// 使用 jchardet 获得文件编码 -javacode
// 当含中文的文件用ANSI编码保存时，检测还是出错。

import java.io.BufferedInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;

import org.mozilla.intl.chardet.nsDetector;
import org.mozilla.intl.chardet.nsICharsetDetectionObserver;

/**
 * 借助JCharDet获取文件字符集
 * 
 * @author 网上代码 PS: JCharDet 是mozilla自动字符集探测算法代码的java移植，其官方主页为： http://jchardet.sourceforge.net/
 * @date 2008/11/13
 */
public class FileCharsetDetectorUtil {

    private boolean found = false;

    /**
     * 如果完全匹配某个字符集检测算法, 则该属性保存该字符集的名称. 否则(如二进制文件)其值就为默认值 null, 这时应当查询属性
     */
    private String encoding = null;

    public static void main(String[] argv) throws Exception {
        // String encoding = new FileCharsetDetector().guestFileEncoding("E:/Song/" +
        // "Alison krauss-When you say nothing at all.mp3");
        // System.out.println(encoding);
    }

    /**
     * 传入一个文件(File)对象，检查文件编码
     * 
     * @param file File对象实例
     * @return 文件编码，若无，则返回null
     * @throws FileNotFoundException
     * @throws IOException
     */
    public String guestFileEncoding(File file) throws FileNotFoundException, IOException {
        return geestFileEncoding(file, new nsDetector());
    }

    /**
     * 获取文件的编码
     * 
     * @param file File对象实例
     * @param languageHint 语言提示区域代码 eg：1 : Japanese; 2 : Chinese; 3 : Simplified Chinese; 4 :
     *        Traditional Chinese; 5 : Korean; 6 : Dont know (default)
     * @return 文件编码，eg：UTF-8,GBK,GB2312形式，若无，则返回null
     * @throws FileNotFoundException
     * @throws IOException
     */
    public String guestFileEncoding(File file, int languageHint) throws FileNotFoundException,
            IOException {
        return geestFileEncoding(file, new nsDetector(languageHint));
    }

    /**
     * 获取文件的编码
     * 
     * @param path 文件路径
     * @return 文件编码，eg：UTF-8,GBK,GB2312形式，若无，则返回null
     * @throws FileNotFoundException
     * @throws IOException
     */
    public String guestFileEncoding(String path) throws FileNotFoundException, IOException {
        return guestFileEncoding(new File(path));
    }

    /**
     * 获取文件的编码
     * 
     * @param path 文件路径
     * @param languageHint 语言提示区域代码 eg：1 : Japanese; 2 : Chinese; 3 : Simplified Chinese; 4 :
     *        Traditional Chinese; 5 : Korean; 6 : Dont know (default)
     * @return
     * @throws FileNotFoundException
     * @throws IOException
     */
    public String guestFileEncoding(String path, int languageHint) throws FileNotFoundException,
            IOException {
        return guestFileEncoding(new File(path), languageHint);
    }

    /**
     * 获取文件的编码
     * 
     * @param file
     * @param det
     * @return
     * @throws FileNotFoundException
     * @throws IOException
     */
    private String geestFileEncoding(File file, nsDetector det) throws FileNotFoundException,
            IOException {
        // Set an observer...
        // The Notify() will be called when a matching charset is found.
        det.Init(new nsICharsetDetectionObserver() {
            public void Notify(String charset) {
                found = true;
                encoding = charset;
            }
        });

        BufferedInputStream imp = new BufferedInputStream(new FileInputStream(file));

        byte[] buf = new byte[1024];
        int len;
        boolean done = false;
        boolean isAscii = true;
        boolean hasVerifyUnicodeEndian = false;
        byte firstByte = 0,secondByte = 0;

        while ((len = imp.read(buf, 0, buf.length)) != -1) {
            // Check if the stream is only ascii.
            if(len >= 2 && !hasVerifyUnicodeEndian){
                firstByte = buf[0];
                secondByte = buf[1];
                hasVerifyUnicodeEndian = true;
            }
            if (isAscii)
                isAscii = det.isAscii(buf, len);

            // DoIt if non-ascii and not done yet.
            if (!isAscii && !done)
                try {
                    done = det.DoIt(buf, len, false);
                } catch (Exception e) {e.printStackTrace();}
        }
        det.DataEnd();

        if (isAscii) {
            encoding = "ASCII";
            found = true;
        }
        imp.close();
        if (!found) {
            String prob[] = det.getProbableCharsets();
            if (prob.length > 0) {
                // 在没有发现情况下，则取第一个可能的编码
                encoding = prob[0];
            } else {
                return null;
            }
        }
        if(encoding.equalsIgnoreCase("UTF-16LE")){
            encoding = "GBK";
        }else if (encoding.equalsIgnoreCase("windows-1252") && firstByte == -1 && secondByte == -2) {//Unicode Little-endian
            encoding = "UTF-16LE";
        }
        return encoding;
    }
}
